Last updated: May 3, 2025
Being aware of the UV Index is crucial for residents of Iruma, Japan, where sunny days can lead to varying levels of ultraviolet radiation. Understanding UV levels is essential for preventing sunburn and protecting skin health, especially during peak hours when the index reaches a maximum of 11 between 11:00 AM and 1:00 PM. With Iruma's Cfa climate, characterized by warm summers and ample sunshine, the risks of UV exposure can escalate quickly. Stay informed and safeguard your skin by monitoring the UV Index and taking appropriate precautions.
The UV Index throughout the day shows a stark rise as the sun climbs higher in the sky. Starting at a modest 2 at 07:00, it quickly escalates, hitting 5 by 08:00. The peak occurs between 11:00 and 12:00, reaching a significant 11, indicating a high risk for damage from unprotected sun exposure. As the afternoon progresses, the index gradually decreases, dropping to 9 at 13:00 and further to 7 by 14:00. By late afternoon, the UV levels decline sharply, returning to 5 at 15:00, followed by a mere 2 at 16:00. As the sun sets, the UV Index falls to 1 at both 17:00 and 18:00, and finally reaches 0 by 19:00, signaling a safe end to sun exposure for the day. Be cautious during the midday hours when the sun's rays are strongest!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 5 | moderate | 30 min |
| 09:00 | 7 | high | 25 min |
| 10:00 | 9 | very high | 15 min |
| 11:00 | 11 | extreme | 10 min |
| 12:00 | 11 | extreme | 10 min |
| 13:00 | 9 | very high | 15 min |
| 14:00 | 7 | high | 25 min |
| 15:00 | 5 | moderate | 30 min |
| 16:00 | 2 | low | 45 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 0 | low | 45 min |
Throughout the year, seasonal changes in UV Index reveal significant variations in sun exposure risk. The high-risk months for UV exposure are predominantly from March to August, with the peak occurring in May, June, July, and August, where the UV Index reaches 11, categorized as extreme with a burn time of just 10 minutes. During this period, individuals are strongly advised to take precautions such as wearing sunscreen, protective clothing, and seeking shade, especially between 10 AM and 4 PM, when UV radiation is at its strongest. In contrast, the UV Index indicates moderate levels in January, November, and December, and high levels in October and February—months where sun safety should still be observed, though the urgency is somewhat reduced.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sapporo UVI | 2 | 3 | 6 | 7 | 9 | 9 | 9 | 10 | 8 | 5 | 3 | 2 |
| Yokohama UVI | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Tokyo UVI | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Iruma | 4 | 6 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Nagoya UVI | 4 | 6 | 8 | 10 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 3 |
| Osaka UVI | 4 | 6 | 8 | 11 | 11 | 11 | 12 | 11 | 10 | 7 | 5 | 3 |